The purpose of this project is to examine the enzymology of nuclear protein phosphorylation in normal human colon and colon carcinoma. Present efforts have focused on normal rat liver and rat colon nuclei for the purpose of working out enzyme isolation techniques for the nuclear protein kinases. An enzyme has been found in rat liver nuclei which is histone-specific and is enriched 50-fold over nuclei. The rat colon enzyme preparation is initially preferentially chromatin-bound and prefers casein as substrate. The colon enzyme is now 15-fold purified with reference to the original nuclear homogenate.